Automatic control for stokers



Dec; 4, 1934. v :1. ML TERRY AUTOMATIC CONTROL FOR STOKERS Filed Dec. 8. 1931 INVENTOR CHARL S M. TER Y QM W ATTOR Y T Patented Dec. 4, 1934 UNITED STATES 1,983,416 AUTOMATIC CONTROL FOR- STOKERS Charles M. Terry, Decatur, lll., assignor to A. W. Cash Company, Decatur, 11]., a corporation of Delaware Application December 8, 1931, Serial No. 579,758 9 Claims. (Cl. 236-26) This invention relates to the automatic control of stokers, and more particularly to a method and apparatus for controlling the operation of hydraulic stokers automatically in accordance with the demand for heat.

Hydraulic stokers usually comprise a reciprocable ram arranged to feed, fuel from a hopper into a furnace. The ram is driven by means of a hydraulic motor, such as a piston slidable with- M in a cylinder, and a suitable liquid is-supplied 'under pressure to the cylinder by means of a pump. The liquid is usually drawn from a suitable reservoir. Such stokers are frequently installed in connection with steam generating fur- 15 naces.

It has already been proposed to control the speed of hydraulic stokers by connecting the pump directly to the hydraulic motor and providing a by-pass pipe leading from the pump discharge to the liquid reservoir, a valve in the by-pass pipe being connected to a regulator operated by the steam pressure. When the steam pressure increases, the regulator opens the valve and bypasses a portionof the liquid discharged by the pump, thus reducing the speed of the stoker. Certain serious difliculties are encountered in such a system. The opening of the by-pass valve greatly reduces the pressure on the hydraulic motor, and if the stoker ram happens to stick in its casing or becomes blocked by a lump of fuel, as

frequently happens, the reduced pressure will increase but slightly and maybe insufficient to operate the stoker.

As'a result the stoker will stall and the feed of fuel will cease entirely. The flow of air to the furnace will continue, however, and the fuel within the furnace may therefore become consumed to a large extent, thus exposing metal parts of the stoker to the intense furnace heat and caus- 40 ing their rapid destruction.

It is accordingly the main object of the invention to overcome these difficulties and to provide a simple and inexpensive method and apparatus for controlling the operation of a; hydraulic stoker, whereby the fuel feed may be regulated inaccordance with the demand for heat, and the stoker may be operated at a reduced capacity without stalling. It is a further object of the invention to provide a method and apparatus for regulating a hydraulic stoker whereby .ample hydraulic pressure will be available at all times to ensure satisfactory operation of the stoker at any desired speed.

55 It is a further object of the invention to provide simple and inexpensive apparatus for controlling the combustion of fuel in a steam generating furnace fired by a hydraulic stoker, whereby the fuel and air may bedelivered to the furnace in the correct quantities at all times, and whereby .60 eflicient combustion of the fuel may be obtained.

With these and other objects.in view as will be apparent to those skilled in the art, the invention resides in the combination of parts and the steps of the process set forth in the specification and covered by the claims appended hereto.

In accordance with my invention, I provide a hydraulic stoker having a motor which is operated by liquid under pressure, the liquid being preferably supplied from a reservoir by means of a suitable pump. An adjustable valve is connected in series with the stoker motor, and I adjust the size of the valve opening in accordance with the demand for heat. I preferably maintain the liquid at the discharge of the pump at a substantially constant pressure, so that ample pressure is always available to operate the stoker. In the preferred construction, a relief. valve is connected to the pump discharge and arranged so to open at a predetermined pressure, thereby bypassing to the reservoir the unused portion of the liquid discharged by the pump. In the specific embodiment'disclosed, not only the stoker control valve but alsothe air flow dampers are con- 35 trolled by a fluid pressure which is-arranged to vary in accordance with the steam pressure but to a considerably amplified extent.

Referring to thedrawing illustrating one .embodiment of the invention, the single figure illustrates somewhat diagrammatically, and partly in section, an arrangement for controlling the operation of a hydraulic stoker installed in connection with a steam generating furnace.

The embodiment illustrated comprises a steam generating furnace 10 having a steam discharge pipe 11. The furnace 10 is fired by means of a hydraulic stoker 12 having a fuel hopper 14 and a hydraulic motor 15. Air for combustion is supplied by means of a fan 16 connected to the fur- 10 nace by a duct 18 having an adjustable damper 19 therein. The gaseous products of combustion leave the furnace through an uptake 20 provided with an adjustable damper 21..

The stoker 12 is operated by a suitable liquid, such as oil, which is supplied under pressure to the hydraulic motor 15 by means of a pump 23. I have illustrated a pump-of the rotary type, which may be driven from any suitable source of power, such as an electric motor (not shown) The pump 11o is arranged to withdraw oil from a reservoir 24 through a suction pipe 25, and discharge the oil through a pipe 27 which connects with a pipe 28 leading to the lwdraulic motor 15. The oil which is exhausted from the motor 15 is returned to the reservoir 24 by means of a pipe 29.

The speed of the stoker 12 and the rate of fuel feed are dependent upon the rate at which oil is supplied to the hydraulic motor 15. and this supply is controlled by means of an adjustable valve 31 which is connected in series with the motor so that the rate of flow through the valve will be the same as through the motor. In the embodiment illustrated this valve is located in the pipe 28. This valve 31 as illustrated comprises a hollow vertically slidable valve member 32 of the balanced type. The valve member 32 is normally stationary but is arranged to be adjusted automatically in accordance with the pressure in the steam pipe 11 by a mechanism to be described hereinafter.

It will be noted that the stoker motor 15, the valve 31, the reservoir 24 and the pump 23 are all connected into a closed circuit. i

It is desirable to maintain ample oil pressure at the pump discharge even when the valve 31 is nearly closed and the stoker is operating at a slow speed, since this pressure may be needed at any time to overcome sticking or blocking of the stoker ram. Too high a pressure will however tend to overload the pump and its driving motor. In

the preferred construction I have illustrated a relief valve 34 which is actuated in accordance.

with the oil pressure at the pump discharge and arranged to open whenever this pressure exceeds a predetermined value. This relief valve is located in a b'y-pass pipe35 leading from the pump discharge pipe 27 to .the oil reservoir 24.

The relief valve 34 may be of various types, but preferably comprises a slidable valve member 3'7 actuated by a flexible diaphragm 38 which is exposed to the pump discharge pressure. The diaphragm 38 is loaded by a compression spring 39 which tends to close the valve. So long as the pump 23 supplies oil at a rate exceeding the .reduireme'nts of the hydraulic motor 15, the valve 34 will remain open to by-pass the excess oil and still maintain ample pressure in advance of the valve 31 to actuate the stoker in case it becomes stuck or obstructed.

The valve member 32 is preferably adjusted automatically to provide an opening which is dependent in size upon the steam pressure, and for this purpose I have shown a diaphragm chamber 41 having a flexible diaphragm 42 therein. The diaphragm is connected to the valve member 32 by means of a rod 43 and loaded by means of a pair of compression springs 45 which tend to open the valve. The diaphragm 42 is subjected to a fluid pressure which is varied in accordance with the steam pressure and preferably to a considerably amplified extent. I

In order to provide such a variable fluid pressure, I preferably utilize a valve 46 of the type disclosed in my prior Patent No. 1,790,685 granted February 3, 1931. Any suitable fluid, such as city water is supplied under pressure to the inlet of the valve 46 through a pipe 4'7, and the outlet of the valve is connected to a piping system 49 which is connected with the diaphragm chamber 41. A manually adjustable discharge valve 50 is connected with the piping system 49 and is normally slightly open to provide a continuous flow through v .g the valve 46.

The valve 46 comprises a slidable valve member 52 which is actuatedby a pair of diaphragms 53 ars and 54 connected by a rod 56. The diaphragm 53 is considerably larger than diaphragm 54, and is subjected to the steam pressure in pipe 11, this pressure being transmitted through a small pipe 57. The small diaphragm 54 is subjected to the pressure in the piping system 49 on the discharge side of the valve. The large diaphragm 53 is loaded by a compression spring 58, which balances the difference between the forces on the diaphragms and tends to close the valve. With this construction, the pressure in the piping system 49 will have a definite value for a given steam pressure, and will be unaffected by variations in the supply pressure in pipe 47, since the diaphragm 54 will move the valve member 52 to compensate for any such variations. A- change in the steam pressure on diaphragm 53 will produce a greatly magnified change in the pressure in the piping .49, since the area of diaphragm 53 is much greater than that of diaphragm 54, and the magnified change is required before a balancedcondition is restored.

Thefiuid pressure in the piping system 49 is preferably utilized not only for the actuation of the stoker speed control valve 31, but also for the control of the dampers 19 and 21. This is accomplished by providing a pair of cylinders 60 each connected to the piping 49 and each having a slidable piston 61 therein loaded by means of a compression spring 62. The pistons 61 are connected to the dampers 19 and 21-by piston rods 64 and links 65.

The operation of the invention will now be clear from the above disclosure. The pump 23 is driven at a constant speed and delivers oil under pressure through pipes 27 and 28 to the hydraulic motor 15 of the stoker 12, which feeds fuel from the hopper 14 to the furnace 10. Oil is returned from the motor 15 to the reservoir 24 through the pipe 29. The fan 16 delivers air to the furnace for combustion through the duct 18, and the gaseous products of combustion escape through the uptake 20. City water is supplied by pipe 4'1 to valve 46 and after flowing through the valve the water escapes to a drain through valve 50, which is left slightly open. If the demand for heat decreases, the steam pressure in pipe 5'1 will increase, and' diaphragm 53 will serve to move valve member 52 slightly toward its open position, thus increasing the pressure inpiping system 49. A given change in steam pressure will produce an amplified change in the pressure posterior to valve 46, because of the difference in the areas of diaphragms 53 and.54. The increased pressure in pipes 49 will be effective on diaphragm 42 and pistons 61. Valve member 32, damper 21, and damper 19 will therefore move toward their closed positions, decreasing both the fuel feed and the air flow in accordance with the decreased demand for heat. Closingvalve 32 tends to increase the pressure in pipe 27, and since this pressure is effective on diaphragm 38, valve member 3'7 will move toward open position and allow an increased flow in by-pass 35, thus maintaining the pressure substantially constant anterior to valve 31. During normal operation at low rates of combustion, valve 31 will be nearly closed and there will be a considerable pressure drop across the valve. If however the stoker ram be- 4 comes stuck or obstructed, flow through the valve'145 will cease momentarily, the. pressure will equalme on opposite sides of the valve, and the full discharge pressure of the pump will be effective on the motor 15 to start the ram and continue the feeding of fuel. V 1

changes in fuel feed or air flow, thereby obtaining efiicient combustion of the fuel.

Having thus described my invention, claim as new and desire to secure by Letters Patent is:

1. The method of controlling the operation of a hydraulic stoker motor comprising the steps of maintaining a supply of liquid at a substantially constant pressure, allowing liquid to flow from the supply through the motor, throttling the flow, and varying the amount of throttling in accordance with the demand for'heat.

2. The method of controlling the operation of a hydraulic stoker motor .comprising the steps of supplying liquid at a substantially constant rate and pressure, directing a portion of the liquid supply through the motor, by-passing the remainder of the liquid supply, throttling the flow through the motor, and varying the ainount of throttling in accordance with the demand for heat. 3. A control system for a stoker having a hydraulic motor comprising a valve connected in series with the motor, means to force liquid under pressure through said parts, the valve having a normally stationary but adjustable valve member to control the flow therethrough, and means to adjust the valve member automatically in accordance with the demand for heat.

4. A control system for a stoker having a hydraulic motor comprising a valve connected in series with the motor, a pump to force liquid under pressure through said parts, the valve having a normally stationary but adjustable valve member to control the flow therethrough, means to adjust the valve member automatically in accordance with the demand for heat, and a relief valve connected to the pump discharge.

5. A control system for a stoker having a hydraulic motor comprising a pump arranged to supply liquid under pressure at a substantially constant rate, means to direct a portion of the liquid supply to the stoker motor, means to bypass the excess liquid. a valve connected in serice with the stoker motor, the valve having a normally stationary but adjustable valve member to control the flow therethrough, and means to adjust the valve member automatically in accordance with the demand for heat.

circuit, the valve being provided with a normally stationary but adjustable valve member to conwhat'L trol the flow through the valve, means to adjust the valve member automatically in accordance with the demand for heat, and means to maintain a substantially constant charge of the pump.

7. A control system comprising a hydraulic stoker'motor, a valve, a liquid reservoir, a pump, pipes connecting all of said parts into a closed circuit, the valve being provided with a normally pressure at the disstationary but adjustable valve member to cone trol the flow through the valve, means to adjust the valve member automatically in accordance with the demand for heat, a by-pass pipe connecting the discharge of the pump with the liquid reservoir, and a relief valve in the by-pass pipe. v

8. A control system for a stoker having a hydraulic motor comprising a valve connected in series with the motor, a pump to force liquid under pressure through said parts, the valve having a normally stationary but adjustable valve member to control the flow therethrough, a pressure responsive device connected to the valve member, and means to provide a fluid pressure on said device which varies in accordance with the demand for heat.

9. A control system for a stoker having a hy- -draulic motor and a steam generating furnace fired thereby comprising a valve connected in series with the motor, a pump to force liquid under pressure through said parts, the valve having a normally stationary but adjustable valve member to control the flow therethrough, a pressure responsive diaphragm connected to the valve member, a damper to control the flow of air to the furnace, a pressure responsive device connected to the damper, and means to provide a fluid pressure on said diaphragm and said device which varies in accordance withthe steam pressure and to an amplified extent. 

